Kids are not as safe in high chairs as they should be, according to new research.

The number of high chair-related injuries increased by over 22 percent between the years 2003 to 2010, according to the new study published in the journal, Child Pediatrics. About 9,400 injuries related to high chairs are treated yearly in the U.S., and the most common cause of injury is falling from the high chair, which can cause head injuries like concussions.

“We have more than 9,400 injuries a year. That’s a child every hour in this country that’s injured from association with a high chair,” study author Dr. Gary Smith, a pediatrician at Nationwide Children’s Hospital in Columbus, Ohio, told NBC.

The researchers are uncertain why the number of injuries is on the rise, but there are some consistencies in what causes them. For instance, high chair are often placed near another table or counter. When a child falls, the surface they hit is often very hard.

Another cause is parents not putting their kids in high chairs correctly. Oftentimes a child is injured because they climb out of the high chair and fall. The researchers found that two-thirds of the kids were standing or climbing on their chair before they fell, meaning they weren’t strapped in correctly.